Method and apparatus for determining the strike and dip of subsurface strata



June ll, 1940. J HNSQN 2,2()3f730y C. H` O METHOD AND APPARATUS FOR DETERMIHING THE STRIKE AND DIP OF SUBSURFACE STRATA Filed Jan. 27, 1939 2 Sheets-Sheet 1 -4 5 LQ g/l//I/l//l/l/'l/ v C l Q a 25 v v I) 0\* 2 6 v I l J \g 'ff Y' j f V NTOR.

' c. H. JOHNSON METHOD AND APPARATUS FOR DETERMINING THE STRIKE AND DIP OF SUBSURFACE STRATA .June 11, 1940.

Filed Jan. 27, 1939 2 Sheets-Sheet 2 Patented .lune 11, 1940 i METHOD AND APPARATUS FOR DETERMIN- ING THE STRIKE AND DIP SUBSUR- FACE STRATA Curtis n. Johnson, santa Monica, Calif.

Application January 27, 1939, Serial No. 253,128

20 Claims.

This invention relates in general to the art of drilling bore holes in the earth, and in particular it relates to the determination of the strike and dip of the earths strata penetrated by the bore hole.

In general, methods of determining the strike and dip of the material penetrated by a bore hole in the earth have consisted of removing a sample, or core, from the bore hole; determining an azimuthal reference line on the core; determining the apparent amount and direction of the dip of the stratification visible in the core--measured with respect to the axis of the core and to its azimuthal reference line; determining the amount and direction of the deviation of the axis of the core from the vertical; and correcting the apparent amount and direction of dip of the stratiflcation for the deviation of the axis of the core from the vertical to obtain the true dip of the 'stratification in the core. I

It is an object of this invention to provide an improved method and means for determining an azimuthal reference line on the core. It is a further object of this invention to provide a method and means for combining part of the op-` eration of determining an azimuthal reference line on the core with the operation of determining the amount and direction of the deviation of the axis of the Core from the vertical. Another object of this invention is to provide a method and means for magnetically polarizing the material to be cored and to determine the direction in which such polarization takes place. Another object of this invention is to provide a method and means for magnetically polarizing in a predetermined direction the material to be cored. Other aims and objects of the invention will appear from the following description, in which:

Figure 1 shows a section of a bore hole in the 40 earth, and schematic means for lowering apparatus of the invention into the bore hole.

Figure 2 shows a wiring diagram for one form of the apparatus in which the power and the control is supplied from the surface.

Figure 3 illustrates the combination of means for determining the amount and direction of the deviation of the axis of the core from the vertical with the means for magnetically polarizing the material to be cored and determining the di- 50 rection of such polarization.

Figure 4 is a plan view of the scale which is photographed by the means shown in Figure 3.

Figure 5 shows an alternate form of the apparatus by means of which the material to be cored may be magnetically polarized in a pre.

(Cl. Z55-1) determined directionand shows a power control operable in the bore hole rather than from the surface.

Figure 6 is a diagram of wiring useful in connection with the apparatus of Figure 5.

The method of the invention consists in magnetically polarizing the material of theearth in a known azimuthal orientation prior to taking the core; determining the amount and direction of the deviation of the axis of the bore hole from the vertical; removing the core from the earth: determining the orientation in the'core of the .magnetic polarity previously impressed on the core-and thereby determining a known azimuthal line on the core; determining the appar` ent strike and dip of the stratification in the core with respect to the axis of the core and to the aforesaid known azimuthal line on the core; and correcting the aforesaid apparent strike and dip for the aforesaid deviation of the axis of the core from the vertical to obtain the true strike and dip of the stratification in the core.

Referring to Figure 1, formation l is penetrated by a bore hole with walls I'-`l and bottom l". Apparatus to be described below in greater detail is enclosed in pressure tight case 2 which is low-y ered into the bore hole as by cable 3, pulley 4, cable drum 5, and prime mover not shown.

In Figure 2, cable 2 is shown to contain electric conductors 6, 1, and 8, of which 6 and 1 furnish electric current to lamps 9 and l0 and to electro-magnet Il from battery.|2 at the surface via switch I3 and slip rings I 4 and l5 on cable drum 5. Conductors 1 and 8 supply Current to gyroscope I6 from battery I1 at the surface via slip rings I5 and I8. These circuits are intended to be purely conventional except as regards the inclusion of electro-magnet Il therein. The bat tery and means serving the function of switch I3 may be carried by case 2, eliminating the necessity for conductors Corning to the surface. Such an alternate arrangement is shown in Figures 5 and 6.

Referring to Figure 3, a somewhat schematic diagram of means for determining the amount and direction of the deviation of the axis of the bore hole from the vertical is shown in connection with electro-magnet Il, which becomes polarized as shown by the symbols N. S. when energized. The aforesaid means consist of gyroscope I6, gyroscope oriented pointer 20, 'azimuth scale 2|, focussing members 22 and 22', camera 23, bubble box 24, lens system 25-26, and lamps 9 and I0. Further structural details on these means are shown in Figures 3 and 5 of U. S. Patent No'. 1,959,141 issued May 15, 1934-to Elmer A. Sperry, Jr. for Bore hole position indicator.

Pointer 20 and azimuth scale 2l are `shown in 1 plan in Figure 4. In addition to its graduations,

azimuth scale 2l is provided with an index 21 which'is fixed to case 2, and indicates the direction of the north pole of electrofmagnet H when it is energized.

The operation of follows:

Prior to removing'core 23, shown by dotted lines in Figure 1, gyroscope I6 is started, and the orientati'on of pointer 2li is noted. Case 2 and its contents'are then loweredl to the bottom of the bore hole as by the means shown. When the case isin that position, switch i3 is Yclosed momentarily, thus momentarily energizing electromagnet l l and lighting lamps 9 and l0. When electro-magnet ll is energized, a magnetic field is set up in the surrounding earth as schematically shown by lines 29 in Figure 1. The material 'composing core-to-be 28 is thus magnetically polarized in the same azimuthal direction as electromagnet I'Lthis direction being indicated on azimuth scale 2l by index 21.

Most materials composing the earths substrata possess more or less magnetic retentivity, sulcient, as a matter of fact, so that under the in-f fiuence of the natural, relatively weak magnetic field'of the earth they retain enough magnetic polarity topermit the fairly successful use of .methods such as .those described in U. S. Patents` No. 1,792,639; 2,104,752; land 2,105,650, to

determine the original azimuthal orientation of cores by means of the naturally retained magnetic polarity. By the method of this present invention, a magnetic'field greatly in excess of vthat lnormally-present'in the earth may be impressed on core-toghe 28, and thus cores whose materials have'very little retentivity may be successfully oriented.

At the instant when electromagnet l l polarizes core-tofbe 28, lamps 9 and IU light momentarily,

thereby simultaneously photographing pointer 2li,V

Following the above operation, core.- 23 is re' moved by any of the conventional methods.

Upon the removal of ycore 28 to the surface, its magnetic polarity transverse to its axis may be determined. For this purpose I may employ apparatus similar to that describedin U. S. Pat-i l ents No. 1,792,639; 2,104,752; 0r 2,105,650, thOugh such use was not contemplated by the inventors thereof, since the method of my invention of imposing an artificial magnetic polarityin a known direction on the earths substrata to be coredWas not then known.

Having determined the magnetic polarity of the core, and knowing from the above composite photographthe'azimuthal direction of the impressed magnetic polarity, a line of known azi'- muth may be drawn on. the core. Thereafter, by

means Well known to those skilled in the art,l

the apparent strike and dip of the stratification inthe core may be determined, and by further means well known to those skilled in the art the correction for the deviation of the'axis` of the core from the vertical may be made, andthe true the above apparatus is as strike and dip of the stratification in the core Cin calall in one operation, it shouldbe understood that'this is not necessary. It would be just as accurate, ifless convenient, to magnetically polarize the material to be cored and determine the azimuth of such polarization in one step, and determinethe deviation of the axis of the bore hole from the vertical in a `second step. This latter method might be advantageously employed if an independent bore hole survey were made afterthe hole was completed. In this case, the bubble box and the means for photographing the bubble may Figure 3..

The method and means hereinabove described is characterized by its operation to magnetically polarize the material to be cored and detertro-magnet when it is energized. Under some l'circumstances it may be advantageous to magnetically polarized the 'material to be cored in, 'a predetermined direction,` such as True North, Magnetic North, etc. Modified apparatus for this purpose is shown in Figures 5 and 6, in which, incidentally, the circuits are arranged for operationwithout electric conductors coming to the surface.

In Figure 5 electro-magnet H is shown rigidly attached to inner case 30, with which it is rotatively mounted in case 2 as by bearings 3|, 32, and 33. Moto1f34, mounted inside case 2, is arranged to slowly rotate inner case 30 and electromagnet ll with respect tocase 2, as by pinion 'gear 35 and internal ring gear 36.

Gyroscope I6 is mounted within inner case 30 in a manner similar to its mounting in case 2 as shown vin Figure 3. As in Figure 3, pointer 20 is oriented by gyroscope yI and appears in the photographed record together with azimuth scale 2| (similar to azimuth scale 2|) as shown in Figure 4. However, in the modified apparatus of Figures 5 and 6, pointer 20 carries light flexible contact brushes 31, and scale 2| is composed of an electricinsulator and carries contacts 38, which, with brushes 31, form switch 39 of -Figure 6, and act in the electric circuit as Iwill hereinafter be described.- Azimuth scale 2| ts just tightly .enough inside inner case 3llso is placed.l f

' Since, in the modified apparatus of Figures 5 and Gv the power supply is 'contained in case 2,-. switching means for initiating the polarizing and photographing action must be provided. One form which this switching means may take is a switch on the bottom of case 2, shown in Figure 5, and comprising rod 40, flexible water-tight .f diaphragm 4l sealed to case 2 (as by flange 42) and enclosing switch contacts 43 and 44, which together constitute switch 45 of Figure 6, adapted to make Contact when pressure is applied to rod 40.

The operations of polarizing and photographing may best be described in terms of Figure 6, in which elements not heretofore described are self holding relays 46 and 41, and circuit breaker 48. The operation is as follows:

be omitted from the device of During all the time the apparatus is 'in the bore hole, gyroscope I6 is supplied with current from battery 49 via conductors 50, 5I, and 52, and the ground return.

When rod 40, of Figure 5, strikes the bottom of the bore hole switch 45 is closed, at least momentarily. When switch 45 is closed, self holding relay 46, in parallel with switch 45, closes and continues to complete the circuit initially completed by the closing of switch 45`even though switch 45 should thereafter open. Th. circuit so closed supplies current to motor 34 from battery 49 via conductor 50, circuit breaker 48, conductors 53, 54, 55, and 56, self holding relay 46, and the ground return.

As seen in Figure 5, motor 34, being so energized, rotates inner case 30 and electro-magnet Il with respect to case 2. Gyroscope I6 and gyroscope pointer 20, due to the gyroscopic action, do not turn with inner case 36. Thus contacts 38 will rotate until they make contact with brushes 31, thereby closing switch 39 `of Figure 6.

When switch 39 is closed, it would ordinarily have to carry a large current for energizing electro-magnet Il and lighting lamps 9 and I0. To

minimize the current carried by the light flexible brushes of switch 39, switch 39 is paralleled by the switch contact of self holding relay 41. This contact, being of low resistance compared to the brushes of switch 39, carries `most of the current when it is closed by the current carried initially by switch 39.

When self holding relay 41 is closed, electromagnet Il is energized from battery 49 via conductor 50, circuit breaker 48, the tripping coil of circuit breaker 48, self holding relay 41, conductors 51, 58, and 56, self holding relay 46, and the ground return.

When self holding relay 41 is closed, current is also supplied to lamp I from battery 49 via conductor 50, circuit breaker 48, the tripping coil of circuit breaker 48, self holding relay 41, conductors 59, 60, 6I, 62, 55, and 56, self holding relay 46 and the ground return.

When self holding relay 41 is closed, current is also supplied to lamp 9 from battery 49 via conductor 50, circuit breaker 48, the tripping coil of circuit breaker 48, self holding. relay 41, conductors 59, 63, 64, 62, 55, and 56, relay 46, and the ground return.

As soon as the field builds up on the coil of circuit breaker 48, circuit breaker 48 is tripped, whereupon motor 34 comes to a stop, and the current to electro-magnet ll and lamps 9 and I0 is cut off. The period of the build up of the field of the coil of circuit breaker 48 is so chosen `that there is suflicient time for the field of electro-magnet Il to build up to maximum, and for lamps 9 and I0 to have properly exposed the lm in camera 23.

Though I have described my invention in terms of certain apparatus, it should not be limited thereby, but only by the claims.

I claint: 1. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a polarity on said substrata, determining the direction of said polarity prior to removing a sample from said substrata, removing a sample from said substrata, and determining the direction of said polarity in said sample after removing said sample from said substrata.

self holdingthe steps of impressing a magnetic polarity on said substrata, determining the polarity of said substratamrior to removing a sample from said substrata, and determining the direction of said polarity in said sample after removing said samplel from said substrata.

3. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a magnetic polarity on said substrata, determining the direction of said polarity prior to removing a sample from said substrata, determining the direction of a reference axis in said sample, removing said sample from said substrata, and determining the direction of said polarity in said sample after.` removing said sample from said substrata.

4. The method of determining the strike and `dip of substrata of the earth which includes 5. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a magnetic polarity on said substrata in a known direction, removing a sample from said substrata, and determining the direction of said polarity in said sample after removing said sample from said substrata.

6. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a polarity on said substrata in a known direction, and determining the direction of said polarity in a sample taken fror said substrata.

7. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a magnetic polarity on said substrata in a known direction, determining the direction of a reference axis in a sample of said substrata, removing said sample from said substrata, determining the direction of said polarity in said sample, and determining the amount and direction of dip of the stratification in said sample with respect to said reference axis and the direction of said polarity.

8. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a magnetic polarity on said substrata in a known direction, determining the direction of a reference axis in a sample of said substrata, removing said sample from said substrata, determining the direction of said polarity in said sample, determining the amount and direction of dip of the stratification in said sample with respect to said reference axis and the direction of said polarity, and correcting said amount and direction of dip to refer to the vertical and a horizontal reference line.

9. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a magnetic polarity on said substrata in a known direction, removing said sample from said substrata, determining the direction of a reference axis in the hole from which said sample was taken, determining the direction of said polarity in said sample, and determining the amount and direction of dip of the stratification in`- said sample.

10. Inv combination, means for impressing a remanent polarity in a known direction in a medium surrounding a bore hole and means for determining the direction of said bore hole.

11. In combination, means for impressing a remanent magnetic polarity in a known direction in a medium surrounding a bore hole and .means for determining the orientation of said measuring instrument.

14. In combination, means for impressing a remanent polarity in a medium surrounding a measuring instrument, and means for determining the orientation of the polarization induced in said medium. y

15. In the art of rock sampling, the improvement which comprises the steps of introducing an oriented magnetizer adjacent the rock to be sampled, causing said magnetizer to polarize the rock in the direction of orientation of said magnetizer, and removing a sample of rock which has been so polarized, thereby providing a magnetic index by means of which the original position of the sample in the earth can be determined after removal of the sample.

16. A method of taking rock core samples which comprises impressing an articial polarization in a known direction on the rock to be cored, and removing a core sample retaining said polarization.

17. The method of determining the strike and dip of substrata of the earth which includes the steps of impressing a polarity on said substratain a predetermined direction, removing a sample from said substrata, and determining the direction of said polarity in said sample after the removal of said sample from said substrata.

18. In combination, means Afor impressing a remanent polarity in a medium surrounding a bore hole, and means for orientating said rst named means in a predetermined direction inside said bore hole.

19. In the art of rock sampling, the improve ment which comprises the steps of introducing an oriented magnetiaer adjacent the rock to be sampled, causing said magnetizer to polarize the rock in the direction of orientation of said magnetizer, thereby providing a magnetic index by means of which the original position of a sample removed from such polarized rock can be determined.

20. 'I'he method of determining the strike and dip of substrate. of the earth which includes the steps of impressing a polarity on said substrata in a known direction in the vicinity of a bore hole in said substrate, and determining the direction of a reference axis in said bore hole.

CURTIS H. JOHNSON. 

